The present invention relates to an apparatus and method for fabricating freeform solid shapes using multiple materials and multiple sources.
Rapid prototyping technologies are known which incorporate solid freeform fabrication processes and machines. Such systems build an object layer by layer or point by point under the control of a computer. Typically, a computer-aided design (CAD) file which represents a desired object is sliced into a large number of thin layers, with the contours of each layer being defined to form vectors or polylines. Computer numerical control (CNC) methods are then used to drive a fabrication tool for building the object layer by layer.
Rapid prototyping has found a broad range of applications such as verifying CAD databases, evaluating design feasibility, testing part functionality, assessing aesthetic considerations or ergonomic considerations, creating conceptual models and sales or marketing tools and providing small production runs.
In U.S. Pat. No. 5,121,329, a fused deposition modeling system is disclosed which utilizes a heated nozzle to melt and extrude a nylon wire or a wax rod. The nozzle is moved and controlled by a computer system in accordance with sliced CAD data. This process requires preparation of a raw material into a flexible filament or rigid rod and is unable to utilize high-melting point materials such as metals or ceramics. Other fused deposition modelling systems use particulate compositions dispersed in a binder. The binder is later burned off and the remaining particles are sintered or densified by metal impregnation.
Ballistic particle modelling processes fabricate objects by spraying liquid resin droplets. The resin droplets may be sprayed through an inkjet print head with droplet sizes in the range of 30 to 50 microns. Obviously, high part accuracy may be obtained but only at very slow build rates.
Welding type systems are known where a wire is deposited on a substrate and melted by directed laser energy. The wire is driven from a spool through a nozzle which is controlled by a computer system. In other systems, molten metal is deposited onto a surface by a combination of a moveable electrode and weld torch.
Existing rapid prototyping systems are unable to effectively combine different materials and different sources to create functionally graded compositions or locally controlled properties. Therefore, there is a need in the art for a freeform solid fabrication system which utilizes multiple sources and multiple materials.